fasten on/upon something
phrasal verb with fasten verb uk/ˈfɑː.sən/ us/ˈfæs.ən/
集中注意力于；集中思想于
to give attention to something, because it is of special interest or often because you think it is the cause of a problem
The politician has fastened on the problems of the working poor. 这位政治人物非常关注从业人员中的穷困人群。
My mind fastened on his admission that he was an agent. 我的注意力还集中在他承认自己是间谍的事情上。